Match banner brand, print splash, optional crop, and demo seed (#6)

## Summary
- Rebrand public site, portal, and emails from Ecoprint orange to the PRINTFORGE banner palette (navy / cyan / lime).
- Replace the loading splash with a CSS 3D-print animation; product uploads get a default-on smart crop + background filter checkbox.
- Add `manage.py seed_demo` for client walkthroughs on dev/beta only (refuses prod).

Closes #5.

## Test plan
- [ ] Public pages and buttons are cyan/lime, not orange
- [ ] Splash shows a printer building a model (or a static print if reduced motion)
- [ ] Product edit: smart-crop checked by default; uncheck stores the original photo
- [ ] `uv run python manage.py seed_demo` fills shop, contacts, leads, orders, campaigns
- [ ] `DJANGO_ENV=prod` seed_demo exits with an error

Reviewed-on: #6

site/email_sms/tests.py

@@ -336,7 +336,7 @@ class CampaignSendTests(TestCase):
         self.assertEqual(summary.to, [self.user.email])
         self.assertTrue(mail.outbox[0].alternatives)
         self.assertEqual(mail.outbox[0].alternatives[0][1], "text/html")
-        self.assertIn("#00626c", mail.outbox[0].alternatives[0][0])
+        self.assertIn("#00aeef", mail.outbox[0].alternatives[0][0])
         self.assertTrue(summary.alternatives)